Some fast programs for generating prime numbers, calculating
============================================================
the number of twin primes and Bruns constant
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Author
------

Stefan Spaennare, Lund, Sweden

E-mail: stefan@spaennare.se

Home page:    http://www.spaennare.se/index.html
Program page: http://www.spaennare.se/ssprog.html

First version: 2005-06-06 
Latest update: 2010-03-20


Contents
--------

1. Introduction
2. Important note
3. Compiling instructions
4. References


1. Introduction
---------------

This readme file only covers how to compile the programs in the prime
number package. See the header of each program source code (*.c) for
information how to use the programs, algorithms, benchmarks etc.

The package now comes with some pre-compiled executables with Intel
icc C/C++ 11.1 compiler for 32-bit and 64-bit Linux.

Purpose:

esieve.c: Generating, counting and printing prime numbers.

ptwins.c: Prime number and twin primes statistics.

cbrun.c, cbrun2.c and cbrun3.c: Calculating prime number and
twins primes statistics and Bruns constant (double precision
version).

cbrunl.c, cbrun2l32.c, cbrun3l32.c, cbrun2l64.c and cbrun3l64.c: 
Calculating prime number and twin primes statistics and Bruns 
constant (long double precision versions). Recommended versions 
for large n (>=10^10).


2. Important note
-----------------

It is HIGHLY RECOMMENDED to run the programs cbrunl.c, cbrun2l32.c and
cbrun3l32.c under Linux using GNU C/C++ compiler (gcc) or perhaps better
Intel C/C++ compiler (icc) with long double precision (i.e. LDOUBLE 1
in the source code) for large n (>=10^10). Use the option "-pc80"
with the Intel compiler.

The GNU C/C++ compiler DJGPP (gcc) for DOS under Windows does not support
long double precision for the functions sqrtl(), floorl(), fabsl()
and logl() used by these programs. The author has commented out these
functions in the source code of the programs (the Windows package only),
with precision loss as result.


3. Compiling instructions
-------------------------

The package now comes with some pre-compiled executables with Intel
icc C/C++ 11.1 compiler for both 32-bit and 64-bit Linux.

To compile all the programs (esieve.c, ptwins.c, cbrun.c, cbrun2.c, cbrun3.c, 
cbrunl.c, cbrun2l32.c, cbrun3l32.c, cbrun2l64.c and cbrun3l64.c) using GNU gcc 
run the script (in the GCCSRC directory):

>chmod +x compall-gcc
>compall-gcc

To compile the programs cbrun2l32.c, cbrun3l32.c, cbrun2l64.c and cbrun3l64.c 
using Intel icc (with the "-pc80" option, i.e. 80-bit floating point operands) 
use the script (in the ICC32EXE or ICC64EXE directories):

>chmod +x compall-icc32
>compall-icc32

>chmod +x compall-icc64
>compall-icc64

The "-p3" versions are for Intel Pentium III, "-p4" for Pentium 4 and 
"-c2d" Core 2 Duo/Quad processors. The "-p4" and perhaps also the
"-c2d" versions should work fine also on newer AMD processors. 

Note, both the Intel compiler (icc) and GNU gcc have many optimization
options to play with. Try to find the best ones for your computer.
Type "icc -help" or see the manual pages for gcc for more information.

Note, the 64-bit versions (cbrun2l64.c and cbrun3l64.c are much slower 
than the 32-bit versions on 32-bit computers but comparable in speed
with the 32-bit versions on 64-bit machines.


References
----------

1. The Intel C/C++ 11.1 (icc) compiler (or later versions in the future)
can be downloaded for free (for Linux, about 600 Mbyte) from:

http://www.intel.com

2. The GNU DJGPP C/C++ (gcc) compiler for DOS under Windows 98/2000/XP
can be downloaded for free from:

http://www.delorie.com/djgpp/


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End of readme_p.txt file.